Samples disturbance overestimates phosphorus adsorption capacity in soils under long-term application of pig slurry

Abstract

ABSTRACTGrinding soil for analysis causes the destruction of aggregates and may expose adsorption sites that would not be available for adsorption in the soil with preserved structure. The study aimed to evaluate the adsorption of P in three soils with and without preserved structure, submitted to pig slurry (PS) application for a long time. Three soils (Acrisol, Ferralssol and Nitisol) with contrasting textures and P contents, with and without PS were selected and samples were collected with and without preserved structure in the 0–10 and 10–20 cm layers. The undisturbed soil columns were submitted to continuous flow, for 10–24 h, of 300 mg L−1 P solution and, at regular intervals, aliquots of the resulting solution were collected and the P content was determined. These data were adjusted exponential models to estimate the maximum adsorption of P. The maximum capacity of P adsorption of the soils were 1.4 to 14 times higher in the milled soil samples, making it clear that the destruction of the soil structure, and consequently the porosity and the preferential paths of percolation of the liquids in the soil leads to an overestimation of the soil capacity to adsorb the P applied to the surface.